You must register for Self Assessment if you're self-employed, a partner in a partnership, or have other income to declare. You'll get a Unique Taxpayer Reference (UTR) which you need to file your tax return.

Who must register for Self Assessment?

You must register if you:

Self-employed sole trader - earned more than £1,000 gross income from self-employment
Partner in a business partnership - regardless of income level
Company director - unless only receiving PAYE salary with no other income
Landlord - receive rental income from property
High earner - income over £100,000 (even if all PAYE)
Child Benefit claimant - you or partner earn over £50,000
Foreign income - receive income from abroad
Savings/investments - untaxed income over £10,000
Capital gains - sold assets above the annual exempt amount

Registration deadlines

You must register by 5 October following the end of the tax year in which you started your business or received untaxed income.

Example: If you started self-employment in August 2025 (tax year 2025/26), you must register by 5 October 2026.

Late registration penalties: No automatic penalty for late registration, but you may face penalties if this causes late filing or payment.

What you'll receive

UTR (Unique Taxpayer Reference): 10-digit number sent by post within 10 working days (21 days if abroad)
Activation code: Separate letter with code to activate your online account

Keep your UTR safe - you'll need it for all Self Assessment dealings, applying for mortgages, and some business contracts.

Self Assessment deadlines

Key dates for Self Assessment tax returns.

Register by 5 October: Register for Self Assessment by 5 October following the end of the tax year in which you became self-employed.
Paper return: 31 October: Deadline for paper tax returns (rare now).
Online return: 31 January: Deadline to file online and pay any tax owed.
Payment on account: 31 July: Second payment on account due if you owe more than £1,000.

Late filing means an automatic £100 penalty. Late payment incurs interest and may lead to further penalties. Set reminders well in advance.

Self Assessment registration deadline

Deadline to register for Self Assessment as a sole trader.

Registration deadline: 5 October following the end of the tax year
Example: Tax year 2024/25: Register by 5 October 2025
Who must register: Self-employment income exceeds £1,000 in the tax year
UTR delivery time: Posted within 10 working days (21 days if overseas)
Activation code: Sent separately by post

Unique Taxpayer Reference (UTR) number

What a UTR is, how to find it, and why you need it for Self Assessment.

Your Unique Taxpayer Reference (UTR) is a 10-digit number that identifies you to HMRC for Self Assessment purposes. You will receive it by post after registering for Self Assessment. You need your UTR to file tax returns, set up online Self Assessment, and for some business transactions.

UTR format: 10-digit number
Also known as: Tax reference, Self Assessment UTR
Where to find it: Previous tax returns, HMRC letters, Personal Tax Account, HMRC app
HMRC Self Assessment helpline: 0300 200 3310
Replacement letter time: Up to 2 weeks

Where to find your UTR

Your Personal Tax Account on GOV.UK
The HMRC app
Previous tax returns
Notices to file a return
Payment reminders or statements of account
The letter HMRC sent when you first registered

If you cannot find your UTR, you can call the Self Assessment helpline to have it provided over the phone or request a replacement letter.

Find your UTR number

Government Gateway: HMRC online account

How to set up and use your Government Gateway account for tax services.

The Government Gateway is HMRC's online account system. Required for:

Registering for Self Assessment, VAT, PAYE, or Corporation Tax
Filing tax returns online
Viewing tax accounts
Paying tax online
Claiming tax reliefs or checking repayments

Personal account: For Self Assessment, personal tax code, tax credits
Business account: Separate account for business taxes (VAT, PAYE, Corporation Tax)
Two-factor authentication: Required - use authenticator app or receive codes by text
Access codes: Some services send activation codes by post (10-21 days)

Setting up an account

Go to HMRC online service needed (e.g., register for Self Assessment)
Create Government Gateway user ID - Choose username and password
Provide email address - For account recovery
Set up two-factor authentication - Authenticator app or mobile number
Wait for activation codes (if required) - Posted within 7-21 days

Separate accounts for business

Important Businesses with both personal and business taxes need two separate Government Gateway accounts:

Personal account Linked to National Insurance number for Self Assessment
Business account Linked to company UTR or VAT number

Both cannot be managed through a single Government Gateway login.

Register for Corporation Tax

How to register your limited company for Corporation Tax with HMRC.

Registering a company with Companies House does not automatically register it for Corporation Tax. Separate registration with HMRC is required within 3 months of starting to trade.

When to register

'Starting to trade' means when a company:

Buys, sells, or advertises goods or services
Employs someone
Hires or rents property or equipment
Starts charging for goods or services

Not considered trading: Registering the company name, setting up a bank account, or conducting market research.

Registration deadline: Within 3 months of starting to trade
Penalty for late registration: Penalties apply for late registration - contact HMRC for specific amounts
Corporation Tax UTR: 10-digit Unique Taxpayer Reference sent within 15 working days
Activation code: Posted within 10 working days (21 if abroad)

Registration process

Wait for Companies House confirmation - Company registration number is required
Register for Corporation Tax online - Most new companies are automatically registered when incorporated. If not, use the online service to add Corporation Tax to your business tax account
Provide company details - Company number, business start date, first accounting period end date
Receive Corporation Tax UTR by post within 15 working days
Receive activation code by post within 10 working days (21 if abroad)
Activate online account using UTR and code

What happens after registration

File annual Company Tax Return (CT600): Due within 12 months of year-end
Pay Corporation Tax: Due 9 months and 1 day after year-end
Keep accounting records: For at least 6 years
Annual confirmation: HMRC sends annual reminder when your return is due

Corporation Tax rates 2025/26: 19% on profits up to £50,000 | 25% on profits over £250,000 | Marginal relief between £50,000-£250,000
First accounting period: Can be up to 18 months (typically 12 months)
Payment deadline: 9 months and 1 day after accounting period ends

Check if you need to register

Use HMRC's tool to check if Self Assessment applies to you.
Gather your information

You'll need your National Insurance number, business start date, and business address.
Create Government Gateway account

If you don't have one, create a Government Gateway ID first.
Register online

Complete the online registration - takes about 10 minutes.
Wait for your UTR

HMRC will post your UTR within 10 working days (21 days if abroad).
Activate your account

Use the activation code from the second letter to access Self Assessment online.

Business Context Testing

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Guvnor

Register for Self Assessment

Who must register for Self Assessment?

Registration deadlines

What you'll receive

Check if you need to register

Gather your information

Create Government Gateway account

Register online

Wait for your UTR

Activate your account

Compliance Assistant

🧪 Business Context Testing

◉ Content Graph

Who must register for Self Assessment?

Registration deadlines

What you'll receive

Check if you need to register

Gather your information

Create Government Gateway account

Register online

Wait for your UTR

Activate your account

Related guides in Tax & Finance

Business Context Testing

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